Card stacker having rotatable bumper to stop card travel

ABSTRACT

A document stacker receives incoming cards and slides them along rails into a stacking area. The cards are stopped by a resilient cylindrical bumper protruding above the slide surface of the rails and located at the end of the stacking area. The bumper is free to rotate in the direction of card motion. As additional cards enter the stacker, they wedge between the last previously received card, which is forced against the rails by a card retaining assembly, and the rails, to become part of the card stacker. The card retaining assembly ensures that each incoming card is subjected to essentially the same pressure as every other incoming card as it wedges between the card stack and the rails. A barrel shaped roller and an adjacent guide member having a surface which conforms to the countour of the barrel-shaped roller located at the entrance of the card stacker uniformly bows the central portion of the incoming card away from the last previously stacked document as it slides into place.

United States Patent [191 Del Rio CARD STACKER HAVING ROTATABLE BUMPER TO STOP CARD TRAVEL [75] Inventor: Eddy Humberto Del Rio, Palm Beach Gardens, Fla.

[73] Assignee: RCA Corporation, New York, NY.

[22] Filed: Nov. 16, 1972 [21] Appl. No.: 307,015

[51] Int. Cl... B65h 29/22, B65h 29/70, B65h 31/06 [58] Field of Search 271/71, 87, 80,51, 177, 271/188, 209, 210, 215, 214

[56] References Cited UNITED STATES PATENTS 3,333,843 8/1967 Misbin et al. 271/71 3,087,724 4/1963 Snowdon et a1. 271/71 3,351,341 11/1967 Maring et al. 271/87 OTHER PUBLICATIONS Doolittle et al.; Stacker-Reader Sorter, IBM Technical Disclosure Bulletin, Vol. 13, No. 10, March 1971.

\HBRATOR MEANS [451 Mar. 26, 1974 Primary Examiner-Evon C. Blunk Assistant Examiner-James W. Miller Attorney, Agent, or Firm Edward J. Norton [57] ABSTRACT A document stacker receives incoming cards and slides them along rails into a stacking area. The cards are stopped by a resilient cylindrical bumper protruding above the slide surface of the rails and located at the end of the stacking area. The bumper is free to rotate in the direction of card motion. As additional cards enter the stacker, they wedge between the last previously received card, which is forced against the rails by a card retaining assembly, and the rails, to become part of the card stacker. The card retaining assembly ensures that each incoming card is subjected to essentially the same pressure as every other incoming card as it wedges between the card stack and the rails. A barrel shaped roller and an adjacent guide member having a surface which conforms to the countour of the barrel-shaped roller located at the entrance of the card stacker uniformly bows the central portion of the incoming card away from the last previously stacked document as it slides into place.

6 Claims, 4 Drawing, Figures CARD STACKER HAVINGROTATABLE BUMPER TO STOP CARD TRAVEL BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART This invention relates to document stackers, and in particular, to an improved apparatus for stacking punched cards on edge.

In many apparatuses for stacking documents on edge, an incoming document enters the stacking area, is slid along the surface or face of a previously stacked document, and comes to rest when its leading edge strikes a wall or other stop member at the far side of the stack ing area. The present invention is in part directed to the problem of dissipating the kinetic energy contained by the document or card without damage to the card or stop member, while generating a minimum of acoustical noise, when the card strikes the stop member.

In document stackers of this type, it has been found that, when the documents are punched document, e. g.,

i cards, the sliding of one card along the surface of an other card at high speed often results in a tearing of web areas between punches in either or both of the cards. Additionally, where information is recorded magnetically on magnetic record cards having a magnetic recording surface area thereon, the magnetic recording surface may become scored when one card is slid along the surface of another, thereby destroying the magnetically recorded information.

In the card stacking apparatus described in U.S. Pat. No. 3,333,843, entitled Document Stacker, issued to T]. Misbin on Aug. 1, 1961, and assigned to the same assignee as the present invention, provisions are made to bow the central portion of an incoming card away from the card stack so that is is not slid along the re cording area of the last previously stacked card. The top and bottom edges of-the bowed card serve as runners which ride along top and bottom unpunched or non-information containing portions of the card most recently stacked. The bowing is accomplished by feeding the incoming card between two pinch roller assemblies located at the entrance to the stacking area. The

first pinch roller assembly includes a roller mounted on a shaft. The second pinch roller assembly also includes a roller mounted on a shaft, and, in addition, includes two additional rollers coaxially mounted on opposite sides of the first roller. The two additional rollers have the same diameter. The diameter of the additional rollers is larger than the diameter of the first roller. The two shafts are parallel and are oriented so thatthe top and bottom edges of the bowed incoming card are forced into contact with the slide across the top and bottom unpunched or non-information containing portions of the last previously stacked cards.

When the documents are very flexible, e.g., the cards are heavily punched and the punch pattern is unevenly distributed, the incoming cards tend to bow most in the area where they are most heavily punched rather than symmetrically about their lengthwise center lines. This increases the possibility of card damage since an edge of the incoming bowed card may not ride on the unpunched area of the previously stacked card. Another part of the present invention is an improved bowing apparatus which provides controlled uniform bowing of the incoming cards regardless of the punch pattern so that the edges of bowed incoming cards slide only along the unpunched top and bottom portions of the previously stacked card.

The ever increasing accumulation of incoming cards near the entranceof the stacking area of a card stacker eventually reaches a point where no further cards can enter without becoming jammed. In U.S. Pat. No. 3,351,341, entitled Variable Angle Card Deck Support, issued to BE. Maring et al., on Nov. 7, 19 67 is described a type of card stacker in which cards are dropped vertically on edge on to a base member. Means are provided for pushing the card stack away from the point of entry and increasing the angle of in clination of the card stack away from the angle of card entry as the stack size increases so that the tendency of the deck to fan out will not cause cards to fall over, thereby jamming the stacker. However, in the type of card stacker wherein the cards are slid along the surface or face of a previously stacked card quite a different problem is encountered. Here, care must be taken to maintain a constant back pressure against the incoming card as the size of the card stack increases. The present invention provides an apparatus to ensure that each card is subjected to the same pressure as it enters the card stack.

SUMMARY OF THE INVENTION A resilient cylindrical bumper is located along the path of travel of a guide member upon which objects move and is free to rotate in the direction of object motion. The bumper protrudes beyond the surface of the guide member on which the object moves so that the object is stopped while it imparts rotational motion to the bumper when it strikes against the bumper. In this manner, the kinetic energy of the object is partially absorbed and partially transferred to the bumper. The rotational movement of the bumper ensures that successively stopped objects strike the bumper in random lo cations along its circumference.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a card stacker embodying the invention.

FIG. 2 is a detailed view of section 2 of FIG. 1.

FIG. 3 is a side view of the guide and stop members of the card stacker of FIG. 1.

FIG. 4 is a side view of the base plate and card deck retaining plate assembly indicating, by broken line portions, a position of the retaining plate assembly assumed during the operation of the card stacker and positions of cards within the card stack corresponding to the position of the retaining plate assembly.

DETAILED DESCRIPTION OF THE DRAWINGS The same reference designation number in different figures refers to the same element.

FIG. 1 is a perspective view of a card stacker embodying the invention. Card stacker 10 receives entering cards and manipulates them to form a card stack or deck 12. The outline of the card stack is indicated by broken line 14. Card stack 12 is shown in phantom so as to indicate it is increasing in size as each new card is added, and, to clearly show portions of card stacker 10 which are necessary in understanding the invention. Card 16, entering card stacker 10, represents a typical card in the deck 12. The documents manipulated by card stacker 10 are punched cards as are typically seen in business and scientific data processing applications.

Alternatively, they may be cards coated with a magnetic recording medium upon which information is magnetically recorded. The punched cards have various punch patterns dependent on the code requirements of the specific data processing application. However, each card 16 includes a central information bearing portion 18, in which a plurality of rectangular holes 20 have been punched in accordance with the coded information. Card 16 also includes a top portion 22 and a bottom portion 24, adjacent respectively to the top edge 26 and the bottom edge 28, where there are no punched holes. Since the top and bottom edges, respectively 26 and 28, and the top and bottom portions, respectively 22 and 24, are free of punched holes 20 or otherwise stored information they can be acted upon to manipulate the'cards without damage to the stored information.

Entering card 16 is guided, by means not shown, between pinch roller assemblies 30 and 32. Pinch roller assembly 30 contains two rollers, 34 and 36, having the same diameter, which are fixedly mounted on shaft 38.

Similarly, pinch roller assembly 32 contains two rollers,

and 42, having the same diameter, which are fixedly mounted on sahft 44. The axis of shafts 44 and 38 are parallel. The rollers on each shaft are longitudinally located along the shaft so that they are in alignment with respect to the rollers on the other shaft. Pinch roller assemblies 30 and 32 are spring loaded or otherwise forced together, by means not shown. Either one or both of pinch roller assemblies, 30 and 32 are rotatably driven by drive belts or other suitable means, not shown, so that shafts 32 and 30 rotate respectively in the direction of arrows 46 and 48. An incoming card is pressed between the rollers and driven toward bowing assembly 50.

Bowing assembly 50 comprises barrel-shaped roller 52 and adjacently located curved guide member 54. This portion of card stacker 10 is best understood by simultaneous reference to FIG. 1 and FIG. 2. FIG. 2 is a sectional view of FIG. 1. Barrel-shaped roller 52 is rotatably mounted on shaft 56. The axis of shaft 56 is parallel the axises of shafts 44 and 38. Located at the longitudinal center of barrel shaped roller 52 is groove 58, which circumscribes its entire perimeter. Groove 58 is suitably shaped to guide 0 ring drive belt 60. 0 ring drive belts are so named because their crosssection is circular in shape. 0 ring drive belt 60 is shown broken away for purposes of clarity. 0 ring drive belt 60 may circumscribe a roller, not shown, fixedly mounted on drive shaft 44by which it can be driven. 0 ring drive belt 60, in turn, drives barrel-shaped roller 52. Alternatively, barrel shaped roller 52 may be driven by any suitable means which ensures its angular velocity approximately matches that of rollers 40 and 42.

Adjacent to barrel-shaped roller 52 is curved guide member 54 which has a curved surface 62 adjacent to barrel-shaped roller 52 which conforms substantially to the surface contour of barrel-shaped roller 52. Curved surface 62 extends the entire length (in the direction of motion of incoming card 16) of curved guide member 54. A small gap exists between the surface of barrelshaped roller 52 and cruved surface 62 of curved guide member 54. Curved guide member 54 is wedge shaped, having is narrowest end pointed opposite the direction of motion of incoming card 16. Cruved guide member 54 may be pivoted about shaft 64 with respect to entering card 16 so that it presents minimum interference therewith. Further, curved guide member 54 may be selectively pivoted to receive incoming cards from other devices. An idler roller 66, rotatably mounted on shaft 68, is located in a suitable aperture in curved guide member 54 which is directly opposite groove 58 of barrel-shaped roller 52. Idler roller 68 protrudes slightly from curved guide member 54 and is free to rotate about shaft 68 and serves to facilitate the easy movement of card 16 between barrel-shaped roller 52 and curved guide member 54.

As card 16 moves through bowing apparatus 50, it is bowed in a controlled and uniform fashion and assumes substantially the same contour as curved surface 62 throughout its length. The bowing of incoming card 16 is indicated by the curved shape of card edge 70. The purpose of the bowing is to cause edges 26 and 28 of incoming card 16 to act as runners which slide respectively over unpunched top and bottom portions of the last previously stacked card as the incoming card 16 is moved into juxtaposition with the last previously stacked card in the deck 12. This controlled bowing prevents incoming card 16 from bowing unevenly, thereby ensuring that card edges 26 and 28 may slide along the unpunched portions, respectively 22 and 26, of the previously stacked card. If card edges 26 and 28 were allowed to interact with the edges of the punched rectangular holes, 20, of the previously stacked card it might be torn.

As incoming card 16 is driven forward toward card deck 12 the forward portions of top portion 22 and bottom portion 24 on the side of card 16 facing away from deck 12 come in contact, respectively, with top rail 72 and bottom rail 74 of guide member 76. The forward portion 78 of guide member 76 is wedge shaped so that the incoming card 16 is readily slid along top and bottom rails, respectively 72 and 74, toward deck 12.

Guide member 76 is generally of rectangular shape in accordance with the shape of the document being handled. Rails 72 and 74 are parallel. The front portion 78 of guide member 76 is wedge shaped for the reason stated above. Guide member 76 has a channel 80 to accomodate bowed portion 18 of incoming card 16. A cross-section of guide member 76 is generally U- shaped. In this embodiment, channel 80 is machined as a smooth curved surface, but may alternately be comprised entirely of flat surfaced portions.

Incoming card 16 is slid forward on top and bottom rails, respectively 72 and 74, of guide member 76 without touching the previously stacked cards in deck 12 until it reaches knees 82 and 84, respectively, of rails 72 and 74. Knees 82 and 84 are located at the same point along the length of guide member 76 and mark the end of wedge-shaped portion 78 of guide member 76. Behind knees 82 and 84 the last previously stacked card rests against rails 72 and 74 until incoming card 16 wedges between it and the rails 72 and 74. Card re taining plate assembly 94 ensures that each incoming card 16 is subjected to substantially the same forces as it wedges between the last previously stacked card and rails 72 and 74 as every other incoming card in a man ner that will be described later. It is assumed for the purpose of this description that some cards have been previously stacked. However, if incoming card 16 were the first card to be stacked, card retaining plate 98 would act as the last card previously stacked in the same manner as has been just described.

Inasmuch as incoming card I6 has been bowed inwardly into the U-shaped channel of guide member 76 only its top and bottom edges, respectively 26 and 28, come in contact respectively with the top and bottom portions of the last previously stacked card in deck 12. Incoming card 16, wedging between the last previously stacked card and rails 72 and 74, slides until it is stopped by stop member or bumper 86. When incoming card 16 has come to rest, it has been properly stacked in deck 12.

In prior art card stackers, the incoming cards bump against a fixedly mounted bumper or stop member. Depending on the material from which the bumper is made, and the speed at which the incoming card strikes the bumper, various degrees of damage to the leading edge of the incoming card may be expected. Additionally, the acoustical noise generated by the incoming card striking the stop member is a considerable contribution to the overall acoustical noise level of the entire card stacker. These problems are somewhat alleviated if the bumper is made from a resilient rubber-like material. However, constant usage of the card stacker over a period of time tends to wear away the bumper in one particular spot.

Bumper or stop member 86 can best be understood by concurrent reference to FIGS. 1 and 3. FIG. 3 is a side view of guide member 76 and stop member 86. Reference designations 16a and 16b indicate, respectively, the last previously stacked card and the penultimate previously stacked card in deck 12. Card 16 is, as before, the present incoming card and is shown in FIG. 2 as just abuting stop member 86.

Although card deck retaining plate assembly 94, as will subsequently be described, is designed in an attempt to assure that deck 12 exerts the same pressure on each incoming card 16 so that each incoming card 16 is subjected to the same frictional forces, perfect results are not possible in practical applications. Therefore, it is not possible to adjust the pressure against each incoming card 16 so that each incoming card 16 just barely strikes stop member 86 and comes to rest. Further, each incoming card 16 strikes stop member 86 with a different amount of force than every other incoming card. Stop member 86 is designed to dissipate the kinetic energy contained by incoming card 16 without damage to the card while minimizing the acoustical noise generated as it strikes stop member 86.

Stop member 86 comprises cylindrical roller 88 rotatably mounted on shaft 90 which is afixed to guide member 76. Alternately, shaft 90 may be fixedly connected to cylindrical roller 88 which is in turn rotatably mounted in guide member 76 by means of bearings or the like. Cylindrical roller 88 has an outer layer 92 of a resilient rubber or plastic-like material. Stop member 86 may be, of course, made as one piece from a resilient material. Stop member 86 is mounted so that it protrudes beyond the slide surfaces of rails 72 and 74.

In accordance with the physical mounting of stop member 86 relative to the top and bottom rails, respectively 72 and 74, of guide member 76, any force which is imparted from the leading edge 70 of incoming card 16 when it strikes outer layer 92 of roller 88 results in two component forces. These two forces are the normal force, F directed inward along a radius of cylindircal roller 88, and the tangential force, F perpendicular to the normal force, F and having the direction as indicated in FIG. 3. The normal force, F will result in a slight deformation of outer layer 92 of cylindrical roller 88. The tangential force, F will result in cylindrical roller 88 rotating in the clockwise direction as indicated by arrow 94. In this manner, the kinetic energy of incoming card 16 is partially absorbed by the resilient outer layer 92 of cylindrical roller 88 and partially transferred to cylindrical roller 88 to rotate it. Because of this dissipation, of the kinetic energy of card 16, the edge of incoming card 16 is not damaged as it strikes stop member 86 nor is the acoustic noise generated when incoming card 116 strikes stop member 86 as loud as the acoustic noise generated in prior art card stackers. Furthermore, the rotation of cylindrical roller 88 ensures that cards that subsequently impact on outer layer 92 will impact at various random locations on the circumference of outer layer 92. The rotation of cylindrical roller 88 therefore ensures the even wear ing of outer layer 92 and consequently an increased lifetime of stop member 86.

As previously indicated, the purpose of card retaining plate assembly 94 is to ensure that card deck 12 maintains a constant pressure against the top and bottom rails, respectively 72 and 74, of guide member 76 so that each incoming card 16 is subjected to the same frictional forces as it slides into abutment with stop member 86. During the following description of card retaining plate assembly 94, concurrent reference to FIGS. 1 and 4 will be necessary. FIG. 4 is a side view of the card retaining plate assembly 94 and base plate 96. In FIG. 4, the present incoming card, 116, and the bowing assembly 56 are not shown for reasons of clarity. The broken line portions of FIG. 4 indicate a second position assumed by card retaining plate assembly 94 and positions of cards within deck 12 corresponding thereto.

Card deck 12 rests vertically on base plate 96 and is horizontally retained against guide member 76 by card retaining plate 98. Base plate 96 is free to be vibrated in the direction transverse to the face of the cards in deck 12 by vibrator means 97. Card retaining plate 98 is connected to support arm 1100 which, in turn, is pivotably mounted on sleeve-like member 102 by means of pivot 104. Support arm is suitably contoured to properly couple sleeve'like member 1182 to card retaining plate 98 and to ensure card retaining plate 98 can move easily over base plate 96. Although support arm 100 is shown as an integral part of card retaining plate 98, it may alternately be a separate element which is fixedly connected to card retaining plate 98. Sleevelike I02 contains an inner cylindrical portion K06 which surrounds rod 188 and is made of a material which has a low coefficient of friction. Because of its inner cylindrical portion 106 sleeve-like member 102 is free to move easily along rod I188. Rod 188 is sup ported by suitable means, not shown. Roller its is rotatably mounted via shaft 112 to the end of pivotably mounted support arm 1104 which is not connected to card retaining plate 98. Roller 116 rolls along rail surface 114 of cam H6. The combination of roller mounted on pivotable support arm 104 and riding on cam 116 is. commonly known as a cam-follower in the art. Rail surface llll4 of cam H6 is parallel to base plate 96 in the position designated as 114a, near the entrance to card stacker 1t), and forms a declining ramp in the portion designated as 1114b. The declining ramp typically has a grade of 12 degrees. Metal ribbon 118 is a portion of a negator spring 120. A negator spring is a hclically coiled spring. The center of the coil portion of negator spring 120 is connected to a fixed portion of card stacker 10, not shown. Negator spring 120 pulls sleeve-like member 102 toward guide member 76 with a constant force independently of the distance between sleeve-like member 102 and the point of connection of the center of the coil portion of negator spring 120.

If card stacker has not received any incoming cards 16, card retaining plate 98 rests against the top and bottom rails, respectively 72 and 74, of guide member 76. The first incoming card enters card stacker 10 and wedges between card retaining plate 98 and guide member 76 in the manner previously described and becomes the first card stacked. Each successive incoming card subsequently wedges between the last previously stacked card and guide member 76 in the manner also previously described. In FIG. 4, reference designation 16d indicates the first card stacked, reference designations 16c and 16b indicate, respectively, the next two successively stacked cards, reference designations 16a indicates the last previously stacked card, and reference designation 16a indicates the present incoming card at the present point of operation of card stack 10. As additional cards are stacked, retaining plate 98 is forced toward the left, away from guide member 76. As card retaining plate 98 moves left, roller 110 rides on level portion 114a of rail surface 114. In this portion of rail surface 114, card retaining plate 98 remains substantially perpendicular to base plate 96. When enough cards have been stacked in deck 12, roller 110 begins to ride on declining ramp portion 114 b of rail surface 114. As roller 1 10 begins to ride on declining ramp portion 114b, card retaining plate 98 begins to pivot about pivot 104 and inclines toward the left causing the cards immediately adjacent thereto also incline toward the left. The broken line portion of FIG. 4 indicates a position of retaining'plate assembly 94 when roller 110 has rolled down a substantial portion of declining ramp portion l14b of rail surface 114. Cards 16a through l6n, which are shown in part by broken lines, represent various cards throughout deck 12 when retaining plate assembly 94 has reached the position shown by broken lines. It is to be noted that although the cards immediately adjacent to card retaining plate 98, such as cards 161 through 16n, follow its inclination, the cards immediately adjacent to guide member 76, such as cards 160 through 16d, remain virtually perpendicular to base plate 96. Vibrator means 97 vibrates base plate 96 in a direction parallel to the axis of bar 108 with constant amplitude and frequency. As the cards in deck 12 are tilted toward the left by the actions of retaining plate assembly 94, they tend to move along the direction of vibration away from guide member 76. Thus, the card deck as a whole tends to move toward the left. This leftward movement tends to alleviate the ever increasing pressure of deck 12 against guide member 76, which would, without this leftward motion, make it increasingly more difficult for incoming cards to wedge into place. The leftward movement of the inclined portion of deck 12 can be understood by remembering that it is easier to pull an inclined card which has one edge resting on a flat surface, in the direction of its inclination than it is topush it against the direction of its inclination. That is, the frictional force acting on the card when it is pushed against the direction of its inclination, is greater than the frictional force acting on the card when it is pulled in the direction of its inclination. Although the vibrational movement of base plate 96 is such that it moves to the right as much as it moves to the left, the frictional force, F acting on an inclined card, say l6j, in opposition to its motion as it is pulled to the right is less than the frictional force, F acting on it in opposition to its motion as it is pushed to the left. This imbalance of these frictional forces tends to rectify the vibrational movement of the inclined portion of card deck 12. This portion moves steadily to the left as deck 12 grows. The speed of left-ward motion is a function of the amount of deck inclination. A judicious selection of the angle of the declining ramp portion 114b of cam 116 will ensure that each new incoming card 16 is sub ject to the same pressure from card deck 12 through out the growth of deck 12.

In summarizing the operation of card stacker 10, then, an incoming card 16 is driven toward bowing assembly 50 by pinch roller assemblies 30 and 32 (themselves driven in, the directions indicated by arrows 48 and 46, respectively) between which it is pressed. lncoming card 16 is guided along curved surface 62 of curved guide member 54 into the narrow separation between barrel-shaped roller 52 and curved guide member 54. Bowing assembly 50 uniformly bows incoming card 16 to the contour of the surface of barrelshaped roller 52. The purpose of this bowing is to urge central portion 18 of incoming card 16 inward between rails 72 and 74 of guide member 76 toward channel 80. Incoming card 16 is slid on its top and bottom portions, 22 and 24, respectively, along the portions of rails 72 and 74 in wedge shaped portion 78 of guide member 76 without contacting any portion of deck 12 until it reaches the location of knees 82 and 84.

Deck 12 consists of previously stacked cards and is forced against rails 72 and 74 via the force exerted on card retaining plate assembly 94, against which it rests, by negator spring 120. As the size of deck 12 increases, as additional incoming cards are received, card retaining plate 98 is forced toward the left. This leftward motion causes roller to eventually ride along declining ramp portion 1141; of cam 116. Once roller 110 rides along declining ramp portion 114b of cam 116, retaining plate 98 pivots toward the left about pivot 104 which causes the cards immediately adjacent thereto to incline toward the left. Base plate 96 is vibrated horizontally in the direction of deck growth. The corresponding vibrational motion of deck 12 tends to be rectified in the leftward direction in the inclined portions of deck 12. Therefore the inclined portions of deck 12 tend to move away from the move vertical portions of deck 12 ensuring that the pressure of deck 12 against rails 72 and 74 remains constant as the deck grows.

Having passed the location of knees 82 and 84 of guide member 76, bowed incoming card 16 wedges between the last previously stacked card in deck 12 and rails 72 and 74. Its top and bottom portions, 22 and 24 respectively, continue to slide across rails 72 and 74, respectively, while its top and bottom edges, 26 and 28, respectively, act as runners which slide over the top and bottom portion, respectively, of the last previously stacked card. Central portion 18 of incoming card 16 does not come in contact with the last previously stacked card along the entire length of its travel.

Incoming card 16 comes to rest when it strikes stop member 86. The impact of incoming card 16 against stop member 86 is partially absorbed by the outer resilient layer 92 of stop member 86 and partially trans ferred into the resultant rotational kinetic energy of stop member 86. Because the kinetic energy of incoming card is dissipated in this manner, the damage to incoming card 16 and the acoustical noise generated by the impact is minimized. Additionally, the rotation of stop member 86 ensures the even wearing of resilient outer layer 92.

What is claimed is:

l. A document stacker comprising:

a guide member receptive of incoming documents having two parallel rails and being dimensioned so that first and second portions of said incoming document, adjacent, respectively, to first and second opposite document edges, may slide along said rails;

a resilient cylindrical bumper mounted at a predetermined point along said guide member at which said incoming document is to be stopped and being rotatable in the direction of motion of said incoming document; said cylindrical bumper protruding beyond the slide surface of said rails so that said incoming document is stopped while imparting rotational motion to said cylindrical bumper when said incoming document strikes said cylindrical bumper;

retaining means for urging said incoming document against said rails and for holding previously received documents in a stack against said rails; and

means for bowing the central portion of said incoming documents between said rails away from said retaining means, whereby the edges of each of said incoming documents slide along the top and bottom portions of the last previously received documom, said bowing means including a barrel-shaped roller located at the entrance of said guide member and being rotatable in the direction of incoming document motion,

a curved guide member having a curved surface adjacent to said barrel-shaped roller which conforms substantially to the surface contour of said'barrelshaped roller,

an idler roller mounted in an aperture in said curved guide member protruding just beyond said curved surface and being rotatable in the direction of motion of each of said incoming documents, and

means for guiding said documents between said barrel-shaped roller and said curved surface.

2. The document stacker recited in claim 1 wherein a circumferential groove is located along the length of said barrel-shaped roller and a drive belt is guided in said groove so that said barrel-shaped roller may be driven.

3. The document stacker recited in claim 2 wherein said curved guide member has a wedge-shaped crosssection in the direction of document motion, the thin end of said curved guide member being adapted to receive each of said documents and the thick end of said curved guide member being pivotable about an axis parallel to the axis of said barrel-shaped roller.

4. Th document stacker recited in claim ll wherein said guide member is oriented so that said incoming documents slide horizontally on edge into said stack and said document retaining means includes:

a horizontal base plate to hold said stack;

a retaining plate being horizontally moveable along said base plate and also being pivotable about an axis parallel to said rails to hold said previously received documents within said deck on edge and facewise toward said rails;

means for urging said retaining plate toward said guide member with constant force so that said last previously stacked card presses facewise against said rails;

a cam being generally parallel to said base plate and having a declining ramp portion at a predetermined distance from said guide member;

a cam follower riding on said cam and being coupled to said retaining plate so that retaining plate inclines away from said guide member when said cam follower rides on said declining ramp portion of said cam; and

means for vibrating said base plate horizontally in a direction transverse to said rails.

5. The document stacker recited in claim 4 wherein said means for urging said retaining plate is a helically coiled spring.

6. A document stacker comprising:

a guide member having two horizontal and parallel rails and being dimensioned so that first and second portions of each of said incoming documents, adjacent, respectively, to first and second opposite document edges, may slide along said rails;

a bowing apparatus receptive of :incoming documents including a barrel-shaped roller located at the entrance of said guide member and being mounted to rotate in the direction of motion of said incoming documents, a curved guide member having a curved surface adjacent to said barrel-shaped roller which conforms substantially to the surface contour of said barrel-shaped roller, an idler roller mounted in an aperture in said curved guide member protruding just beyond said curved surface and being rotatable in the direction of motion of said incoming documents, and means for guiding each of said incoming documents between said barrelshaped roller and said curved surface so that the central portion of said incoming document is bowed inward between said rails as said incoming card slides along said rails;

a resilient cylindrical bumper mounted at a predetermined point along said guide member at which each of said incoming documents is to be stopped and being rotatable in the direction of motion of said incoming document, said bumper protruding beyond the slide surface of said rails so that said in coming document is stopped while imparting rotational motion to said bumper when it strikes said bumper; and

a retaining plate assembly including a horizontal base plate to support previously received documents, a generally vertical retaining plate being horizontally movable along said base plate and also being pivotable about an axis parallel to said rails to hold said previously received documents on edge and facewise toward said rails, means for urging said retaining plate toward said guide member with a constant force, a cam being generally parallel to said base plate and having a declining ramp portion at a predetermined distance from said guide member, a cam follower riding on said cam and being coupled to said retaining plate so that said retaining plate inclines away from said rails when said cam follower rides on said declining ramp portion, and means for vibrating said base plate horizontally in a direction transverse to said rails.

#1 l ll l 

1. A document stacker comprising: a guide member receptive of incoming documents having two parallel rails and being dimensioned so that first and second portions of said incoming document, adjacent, respectively, to first and second opposite document edges, may slide along said rails; a resilient cylindrical bumper mounted at a predetermined point along said guide member at which said incoming document is to be stopped and being rotatable in the direction of motion of said incoming document; said cylindrical bumper protruding beyond the slide surface of said rails so that said incoming document is stopped while imparting rotational motion to said cylindrical bumper when said incoming document strikes said cylindrical bumper; retaining means for urging said incoming document against said rails and for holding previously received documents in a stack against said rails; and means for bowing the central portion of said incoming documents between said rails away from said retaining means, whereby the edges of each of said incoming documents slide along the top and bottom portions of the last previously received document, said bowing means including a barrel-shaped roller located at the entrance of said guide member and being rotatable in the direction of incoming document motion, a curved guide member having a curved surface adjacent to said barrel-shaped roller which conforms substantially to the surface contour of said barrel-shaped roller, an idler roller mounted in an aperture in said curved guide member protruding just beyond said curved surface and being rotatable in the direction of motion of each of said incoming documents, and means for guiding said documents between said barrel-shaped roller and said cUrved surface.
 2. The document stacker recited in claim 1 wherein a circumferential groove is located along the length of said barrel-shaped roller and a drive belt is guided in said groove so that said barrel-shaped roller may be driven.
 3. The document stacker recited in claim 2 wherein said curved guide member has a wedge-shaped cross-section in the direction of document motion, the thin end of said curved guide member being adapted to receive each of said documents and the thick end of said curved guide member being pivotable about an axis parallel to the axis of said barrel-shaped roller.
 4. Th document stacker recited in claim 1 wherein said guide member is oriented so that said incoming documents slide horizontally on edge into said stack and said document retaining means includes: a horizontal base plate to hold said stack; a retaining plate being horizontally moveable along said base plate and also being pivotable about an axis parallel to said rails to hold said previously received documents within said deck on edge and facewise toward said rails; means for urging said retaining plate toward said guide member with constant force so that said last previously stacked card presses facewise against said rails; a cam being generally parallel to said base plate and having a declining ramp portion at a predetermined distance from said guide member; a cam follower riding on said cam and being coupled to said retaining plate so that retaining plate inclines away from said guide member when said cam follower rides on said declining ramp portion of said cam; and means for vibrating said base plate horizontally in a direction transverse to said rails.
 5. The document stacker recited in claim 4 wherein said means for urging said retaining plate is a helically coiled spring.
 6. A document stacker comprising: a guide member having two horizontal and parallel rails and being dimensioned so that first and second portions of each of said incoming documents, adjacent, respectively, to first and second opposite document edges, may slide along said rails; a bowing apparatus receptive of incoming documents including a barrel-shaped roller located at the entrance of said guide member and being mounted to rotate in the direction of motion of said incoming documents, a curved guide member having a curved surface adjacent to said barrel-shaped roller which conforms substantially to the surface contour of said barrel-shaped roller, an idler roller mounted in an aperture in said curved guide member protruding just beyond said curved surface and being rotatable in the direction of motion of said incoming documents, and means for guiding each of said incoming documents between said barrel-shaped roller and said curved surface so that the central portion of said incoming document is bowed inward between said rails as said incoming card slides along said rails; a resilient cylindrical bumper mounted at a predetermined point along said guide member at which each of said incoming documents is to be stopped and being rotatable in the direction of motion of said incoming document, said bumper protruding beyond the slide surface of said rails so that said incoming document is stopped while imparting rotational motion to said bumper when it strikes said bumper; and a retaining plate assembly including a horizontal base plate to support previously received documents, a generally vertical retaining plate being horizontally movable along said base plate and also being pivotable about an axis parallel to said rails to hold said previously received documents on edge and facewise toward said rails, means for urging said retaining plate toward said guide member with a constant force, a cam being generally parallel to said base plate and having a declining ramp portion at a predetermined distance from said guide member, a cam follower riding on said cam and being coupled to said retaining plate so that said retaining plate inclines away from said rails when said cam follower rides on said declining ramp portion, and means for vibrating said base plate horizontally in a direction transverse to said rails. 